The present invention relates to an apparatus for performing predetermined processing within a clean room of disc-shaped articles, such as discs to be used for video or audio recording.
Optical recording is widely utilized for recording video, audio and other data, with the recording medium being in the form of discs. In the optical recording method, a photoresist is coated on a glass disc which serves as a substrate, to thereby produce a disc which can be utilized to produce a disc master. Light from a laser beam, focussed to a minute spot, is caused to fall upon the resist film thus formed on the glass disc, in accordance with video or audio data, etc. This process is referred to as the bit-by-bit method of light exposure. The disc is subsequently developed to produce a disc master, in which surface pits are formed whose lengths and repetition period constitute the recorded data.
For convenience of description, a glass disc as described above which is in the condition prior to having a film of photoresist formed thereon will be referred to in the following simply as a glass disc, while a disc which has a film of photoresist formed thereon will be referred to as a resist-coated disc.
With such a method, it is necessary to execute several processing steps in order to prepare a resist-coated disc, i.e. washing of the glass disc, coating the disc with primer (in order to enhance the degree of adherence of the photoresist to the disc surface), photoresist coating, and baking (i.e. thermal processing). During these processing steps, it is essential that all dust be excluded, and for this reason the processing is performed entirely within a clean room. Furthermore, even within the interior of a clean room, minute particles of dust which have not been removed by the filters will remain floating in the atmosphere. In order to prevent these minute dust particles from adhering to the disc surface, a current of air is blown across the glass disc and the resist-coated disc while processing is being carried out on the discs. However it has been found in practice that a sufficiently high degree of dust exclusion effectiveness cannot be attained by such a flow of air alone, due to disturbances which arise within the air flow.
Moreover in the prior art, each of the processing steps described above is executed by a separate processing unit, with the discs generally being manually transferred between these processing units following each processing step. As a result, the overall system size is large, and the rate of productivity is low.